The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the inventors hereof, to the extent the work is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, is neither expressly nor impliedly admitted as prior art against the present disclosure.
The disclosed technology relates generally to the correction of DC noise in signals read by a head of a disk drive. When a low quality head is used to read data signals on a disk drive, the head is subject to instability events. Such head instability events (HIE) manifest themselves as DC noise, which is also referred to as temporary baseline pop. The severity and frequency of the baseline pop is variable. For example, the baseline pop can last for a length of hundreds to thousands of bits and can result in a DC upshift of up to 50% of the amplitude of the envelope of the signal.
Baseline pop resulting from HIEs can cause distortion in both the preamble and the data portion of the signal being read. For example, baseline pop in the preamble portion impacts the acquisition of timing and gain parameters. Baseline pop in the data portion introduces data errors. Furthermore, HIEs may occur in any portion of the disk being read and their occurrence is difficult to anticipate.